The concept of the wireless sensor network (WSN) has already been proposed for a few years. Under the development of modern technologies, the sensors with the capabilities of wireless transmission have already had small size, low cost and the abilities of sensing environmental conditions and processing information. In traditional applications, a large number of wireless sensors are spread over an area, so that a large area can be covered and sensed, and the environmental information collected by these wireless sensors can be transmitted back to the base station for the processing and analysis. However, due to the limitation of the energy consumption, the transmission distance, the signal reception and other restrictions, there are many difficulties and obstacles for the WSN applications.
In order to solve these problems, there are already known technologies exploring the ways to reduce the sensor's power consumption and extend the service life in order to enhance the efficiency of using WSN. The earliest research method is the routing protocol of the Low-Energy Adaptive Cluster Hierarchy (LEACH).
In the LEACH approach, the WSN is divided into several clusters, and a cluster head for each cluster is selected from the several sensors in each cluster. The sensors in each cluster will transmit the data to the cluster head in that cluster, and the cluster head in each cluster will then transmit data to the base station. This cluster-type structure can effectively reduce energy consumption and extend the network lifetime.
In addition, various WSNs based on the clusters have been proposed, some of these WSNs consider the residual energy of the cluster head, some try to find the shortest transmission distance, and some consider the sensing information. After the LEACH is proposed, a routing protocol, called LEACH-Coverage-U, based on LEACH is proposed. In this method, the overlapping area between the sensing area of one sensor and that of another sensor is taken into account, and the sensor with the highest degree of overlapping area with the other sensors is selected as the cluster head for that region. Compared with LEACH, this method is able to further extend the network lifetime.
However, the above mentioned methods still have many deficiencies and blind spots for sensing. Some applications, such as the military inspections, medical cares, and some emergency missions, are not allowed any mistakes happening, and the conventional techniques are not good enough to handle.
For solving the above mentioned problems, the inventors had done a lot of efforts in the analyses, researches and developments, and finally developed the routing method for the wireless sensor network.